updat readme file

Author: dirk.koehler

Readme.md

@@ -1,2 +1,10 @@
 # Arduino library for ultrasonic sensor HC-SR04
-Example can be found in folder Exmples with detailed documentation of code1
+## Description
+This library can be used for the ultrasonic sensor HC-SR04. All measured values are calculated in mm. The main features so far are:
+- public functions
+  - getting one single measurment
+  - getting an average measurement result. count of measurements to calculate average can be set
+  - ask for an obstacle in a givin range. optional caluclate this with an average value
+- if sensor is getting timeout (no echo received), a value of 0 will be returned
+## Examples
+Examples can be found in folder Examples with detailed documentation of code